JP2706561B2 - Valve seat material for internal combustion engine and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve seat material for an internal combustion engine which is particularly excellent in high-temperature wear resistance and is suitable for extending the life thereof, and a method for producing the same.

<Conventional technology> Conventionally, an internal combustion engine using LPG fuel, which is used as a gasoline alternative fuel, is mainly used for taxis, and the mileage per day is about 350 km, which is larger than that of ordinary passenger cars. In particular, the exhaust side valve seat is subject to severe fatigue destructive wear.

In addition, such an LPG internal combustion engine has a problem that specific abrasive wear (mechanical destructive wear) tends to occur and valve seat wear is increased.

For this reason, the present applicants solved lead as described above in pores of a sintered alloy in which a Co-based alloy hard phase was dispersed in a CO-Ni-Mo-C-based iron base in order to solve the above-described problem. The infiltrated material was developed first (see Japanese Patent Application Laid-Open No. 62-10244).

<Problems to be solved by the invention> However, with the demand for higher performance of the internal combustion engine,
In recent years, the LPG internal combustion engine has been required to have a longer life,
The valve seat material is also required to have higher wear resistance at high temperatures.

The present invention has been made in view of the above circumstances, and provides a valve seat material for an internal combustion engine which is particularly excellent in high-temperature wear resistance and is suitable for extending the life thereof, and a method of manufacturing the same. With the goal.

<Means for Solving the Problems> According to the present invention, in order to achieve the above-mentioned object, the total composition is such that the weight ratio of C is 0.3 to 1.5%, Si is 0.1 to 0.8%, and Cr is 1.4 to 4%.
%, Ni0.1 ~ 2%, Mo2.7 ~ 13%, W0.2 ~ 9.5%, Co11 ~ 20%,
V is 0.1 to 2.6% and the balance is Fe, and the structure is 20 to 50% of high-speed tool steel phase in which metal carbide is dispersed, and 10 to 50% of cobalt metal hard phase in which intermetallic compound is dispersed.
20%, and an iron alloy phase containing Co-Ni-Mo-C and an intermediate phase residue in which the cobalt alloy hard phase is diffused into other phases are mixed in a patchy manner. Is characterized by being filled with Pb.

In addition, the present invention is based on the fact that the total composition is C0.3-1.5% by weight,
0.1 to 0.8%, Cr 1.4 to 4%, Ni 0.1 to 2%, Mo 2.7 to 13%, W0.
A method for producing a sintered material having a structure in which phases having different hardnesses are distributed in a patchy manner by 2 to 9.5%, Co 11 to 20%, V 0.1 to 2.6% and the remaining Fe by powder molding and sintering, 0.2-0.7%, Si 1.5-2.5%, Cr 7-9%, Mo 26-30% and balance Co cobalt alloy powder 10-20%, and high speed tool steel powder included in the following Of which at least one is 20-50%, b.C0.7-0.8%, Cr3.8-4.5%, W17-19%, V0.8-1.2
% And Fe remaining, b. C 0.7 to 1.6%, Cr 3.8 to 4.5%, W 11.5 to 19%, V 0.8 to 5.2
%, Co 4.2 ~ 11% and Fe remaining, C 0.8 ~ 1.4%, Cr 3.5 ~ 4.5%, Mo 4.5 ~ 9.2%, W1.5 ~ 6.7
%, V1.6 ~ 4.5% and Fe remaining, D 0.8 ~ 1.4%, Cr3.5 ~ 4.5%, Mo3 ~ 12%, W1.2 ~ 11%, V
0.9 to 3.7%, Co 4.5 to 11% and Fe remaining, Ni 0.5 to 3%, Mo 0.5 to 3%, Co 5.5 to 7.5% and the balance of iron alloy powder of Fe make up a total of 100% It is characterized by using a mixed powder.

(Iron alloy base phase) First, the base phase having the above composition is the same as the alloy described in Japanese Patent Publication No. 55-36242, except that the carbon content is reduced in consideration of increasing the toughness. It is.

The base phases Ni and Mo mainly contribute to strength improvement, and Co is a component for improving high-temperature hardness.

Carbon is added to the alloy powder in the case of the alloy described in Japanese Patent Publication No. 55-36242, but in the alloy according to the present invention, carbon is added in the form of graphite powder in order to improve powder compressibility. Alloy during sintering. The hardness of the base phase is MHV3
It is about 00-380.

(High-speed tool steel phase) Particles of high-speed tool steel are effective in preventing fatigue-destructive wear, and are effective at more than 20%. However, when over 50%, abrasive wear is promoted and wear resistance is increased. At the same time, the mating member is worn down.

High-speed tool steels include Mo-based and W-based as specified in the Japanese Industrial Standards, but both exhibit an effect on wear resistance.

This high-speed tool steel phase shows a structure in which granular metal carbides are dispersed, and its hardness is slightly harder than that of the base phase.
MHV is about 360 to 520.

 Note that Si and Ni may be included as impurities.

(Cobalt Alloy Hard Phase) The hard particles are alloys described in JP-A-62-10244. Among the intermetallic compounds disclosed, Mo33-36%, S
i4-12% cobalt alloy is suitable.

In particular, in the LPG fuel engine, since the interface between the valve and the valve seat is dry, abrasive wear caused by contact between the materials is likely to occur, but the Co-based alloy hard particles are effective in reducing the wear.

The base structure is a structure in which the above-mentioned intermetallic compound is dispersed, and has a hardness of about MHV 800 to 970.

The hard phase in which the intermetallic compound is dispersed partially diffuses into the adjacent iron alloy base phase or high-speed tool steel phase,
It forms an intermediate phase in which properties such as composition and hardness are graded.

With this configuration, the strength of the hard material increases, and the wear resistance can be improved.

When the addition amount of the Co-based alloy hard particles is 5% or more, the abrasion resistance is stable, and preferably 10 to 20%. However, the addition amount exceeding 25% has no effect on cost.

(Lead) The above-described material in which the pores of the sintered alloy according to the present invention are impregnated with lead has a solid lubricating effect at an ambient temperature lower than the melting point of lead, and improves wear resistance.

<Function> According to the present invention, Co-based alloy hard particles in which an intermetallic compound is dispersed and high-speed tool steel particles in which a metal carbide is dispersed are dispersed in an iron matrix containing Co-Ni-Mo-C. In addition, because it is configured to provide an intermediate phase in which part of the Co-based alloy hard particles are diffused into other particles, it is particularly excellent in high-temperature wear resistance and extends its life, and is used for internal combustion engines. It is suitable as a valve seat material.

<Example> Hereinafter, the present invention will be described with reference to examples.

Example-1 0.6% of graphite powder and 0.8% of zinc stearate were added to iron alloy powder having a composition of 6.5% Co-1.5% Ni-1.5% Mo,
Furthermore, cobalt alloy powder of 28% Mo-8.5% Cr-2% Si and 4.2%
% Cr-5% Mo-6.2% W-1.9% V-0.7% Si-1.1% C
Mixed powders were prepared by changing the amount of high-speed tool steel powder equivalent to JIS standard SKH51 in various ways.

The mixed powder was formed into a ring at a pressure of 8 t / cm ² and then sintered in a reducing atmosphere at a temperature of 1200 ° C. for 30 minutes.

Some sintered materials were impregnated with vacuum and high pressure lead at 550 ° C. and 8 atm.

The microstructure of the sintered body is a mixture of a sorbite-like iron matrix, a high-speed tool steel phase in which metal carbide is finely dispersed, and a Co-based alloy hard phase in which intermetallic compounds are dispersed like a maze. An intermediate phase in which a part of the Co-based alloy hard phase diffused into the iron matrix or the high-speed tool steel phase is observed.

The wear resistance of these sintered materials was measured using a simulated engine tester to measure the effects of the cobalt alloy hard phase and the effects of the high-speed tool steel.

The above test machine is a mechanism that drives the camshaft with a motor while heating the valve and valve seat to a predetermined temperature with LPG fuel gas. The temperature, the number of valve reciprocations, the spring pressure of the valve, etc. can be set arbitrarily. It can perform severe tests in a short time.

The test conditions were 6000 valve reciprocations / minute, seat temperature.
The test was performed at 300 ° C for 50 hours, and 21-4N was used as the valve material.

FIG. 1 shows the amount of wear of the valve seat sample, and FIG. 2 shows the amount of wear of the valve.

It can be seen that when the amount of the cobalt alloy hard phase is 10 to 20%, both the valve and the valve seat have less wear.

When the amount of the high-speed tool steel phase is 20 to 50%, the valve seat wear is small, and when the valve wear is 50% or less, the wear is small.

Table 1 shows the wear test of the samples shown in FIG. 1 in which the amount of the cobalt alloy hard phase was 10% and the same sintered body impregnated with lead. The results are shown.

As is clear from the measurement results, it can be seen that abrasion decreases when lead is infiltrated.

Example 2 In addition to the various powders used in Example 1 above, seven types of high-speed tool steel powders having different compositions were prepared.

(1) SKH-2 equivalent composition; Fe-0.8% C-4.1% Cr-17% W-0.9% V (2) SKH-4 equivalent composition; Fe-0.8% C-4% Cr-18% W-1.1 % V-10% Co (3) SKH-10 equivalent composition; Fe-1.5% C-4% Cr-12% W-4.5% V-4.5% Co (4) SKH-51 equivalent composition; Fe-0.8% C -4.2% Cr-6.2% W-1.9% V-50% Mo (5) SKH-57 equivalent composition: Fe-1.3% C-4% Cr-10% W-3.2% V-3.3% Mo-1
0% Co (6) SKH-58 equivalent composition; Fe-1.0% C-4% Cr-1.9% W-1.8% V-8.5% Mo (7) SKH-59 equivalent composition; Fe-1.1% C-4% Cr-1.5% W-1.1% V-10% Mo-
8% Co Co-Ni-Mo iron alloy powder, graphite powder 0.6%, zinc stearate 0.8%, cobalt alloy powder 15% and high-speed tool steel powder 40%, the type of high-speed tool steel powder Produced mixed powders different from each other.

It was formed into a ring shape in the same manner as in Example 1, and sintered at a temperature of 1200 ° C. for 30 minutes in a reducing atmosphere.

Each sintered body was processed into a valve seat shape after lead infiltration in the same manner as described above.

This valve seat sample was assembled on the exhaust side of a propane fuel engine, and operated at an engine speed of 6000 rpm and full load for 500 hours, and the wear amount of the valve seat was compared.

 Table 2 shows the measurement results.

The comparative material was obtained by subjecting a sintered body having a composition obtained by removing the high-speed tool steel phase from the above sample to lead infiltration, and corresponds to the conventional material described in JP-A-62-10244.

Invention materials 1 to 7 correspond to the numbers of the above high-speed tool steel powder.

Inventive materials 1 to 7 are all superior in the reduction rate of the valve seat wear amount as compared with the comparative material which is the conventional material.

Further, among the invention materials 1 to 7, the samples to which the molybdenum-based high-speed tool steel powder of the invention materials 4 to 7 are added have a small wear amount.

<Effects of the Invention> As described above, according to the present invention, Co-Ni-Mo
In the iron base containing -C, while dispersing the Co-based alloy hard particles in which the intermetallic compound is dispersed and the high-speed tool steel particles in which the metal carbide is dispersed, a part of the Co-based alloy hard particles is replaced with other particles. By providing a structure in which an intermediate phase diffused into the steel is provided, abrasive wear and fatigue-destructive wear can be made less likely to occur, and the performance of an engine of an automobile or the like can be improved.

Therefore, it is possible to provide a valve seat material for an internal combustion engine which is particularly excellent in high-temperature wear resistance and is suitable for extending the life thereof, and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a graph showing the amount of wear of the valve seat, and FIG. 2 is a graph showing the amount of wear of the valve.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Akira Fujiki, inventor Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Ichiro Tanimoto 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Katsuhiro Kishi Inventor Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-62-167858 (JP, A) JP-A-2-163350 (JP, A) JP-A-2-8350 (JP, A)

Claims (3)

(57) [Claims] (1) The total composition is C 0.3-1.5% by weight, Si 0.1-
0.8%, Cr 1.4-4%, Ni 0.1-2%, Mo 2.7-13%, W 0.2-9.
5%, Co 11 ～ 20%, V0.1 ～ 2.6% and the balance Fe and the structure is high speed tool steel phase 20-50% in which metal carbide is dispersed and cobalt synthesis in which intermetallic compound is dispersed Hard phase 10-20
%, And an iron alloy phase containing Co-Ni-Mo-C and an intermediate residue obtained by diffusing the cobalt alloy hard phase into other phases are mixed in a patch-like manner. Wood. 2. The valve seat material for an internal combustion engine according to claim 1, wherein the pores are filled with Pb. 3. The composition according to claim 3, wherein the total composition is C0.3-1.5% by weight and Si0.1
~ 0.8%, Cr1.4 ~ 4%, Ni0.1 ~ 2%, Mo2.7 ~ 13%, W0.2 ~
9.5%, Co11 ~ 20%, V0.1 ~ 2.6% and the balance of Fe, the method of manufacturing a sintered material having a structure in which phases having different hardnesses are distributed in a patchy manner by powder molding or sintering. 0.7%, 1.5 to 2.5% of Si, 7 to 9% of Cr, 26 to 30% of Mo, and 10 to 20% of cobalt alloy powder of Co, and at least one of the following high-speed tool steel powders included in the following items (1) to (2): 20-50% for 1 type, C0.7-0.8%, Cr3.8-4.5%, W17-19%, V0.8-1.2
% And Fe remaining, b. C 0.7 to 1.6%, Cr 3.8 to 4.5%, W 11.5 to 19%, V 0.8 to 5.2
%, Co 4.2 ~ 11% and Fe remaining, C 0.8 ~ 1.4%, Cr 3.5 ~ 4.5%, Mo 4.5 ~ 9.2%, W1.5 ~ 6.7
%, V1.6 ~ 4.5% and Fe remaining, D 0.8 ~ 1.4%, Cr3.5 ~ 4.5%, Mo3 ~ 12%, W1.2 ~ 11%, V
0.9 to 3.7%, Co 4.5 to 11% and Fe remaining, Ni 0.5 to 3%, Mo 0.5 to 3%, Co 5.5 to 7.5% and the balance of iron alloy powder of Fe make up a total of 100% A method for producing a valve seat material for an internal combustion engine, comprising using a mixed powder.